SCSI-3 Cable Questions
Gerry_Houlder at notes.seagate.com
Tue Dec 5 09:26:55 PST 1995
I believe the intent of the signal placement guidelines (that specify which
pairs go into which layers) is that it is more important to specify the layers
for S/E use rather than Differential use. The S/E signals are more sensitive to
crosstalk and impedence variations, and the S/E impedence value is much lower
than the differential impedence value.
Thus when the resulting round cable is used in a S/E system, the REQ and ACK
have the proper seperation from the data lines to prevent crosstalk problems.
When that same cable is used with differential drivers, the crosstalk and
impedence variance problems are small enough to not matter; therefore the REQ
and ACK don't have to be in the core.
Do you have any issues with this, other than just to make sure the committee
wasn't misstating its intent?
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